The word Kushan derives from the Chinese term Guishang, used in historical writings to describe one branch of the Yuezhi—a loose confederation of Indo-European tribes that had been driven out of Northwestern China in 176–160 BC, migrated south, and reached Bactria Tajikistan and Northwest Afghanistan around 135 BC.

Kushan Empire during Kanishka's Rule

During the Kushan period in the first to third centuries CE, political, economic, religious, and cultural contact between South Asia and Central Asia greatly accelerated. Archaeological excavations, art, historical evidence, coins, and inscriptions directly reflect connections between the establishment of the Kushan Empire, long-distance trade and cultural transmission between the Northwestern Indian subcontinent and the silk routes. New material evidence has recently come to light that allows Kushan chronological and genealogical issues to be clarified. These historical developments gain added significance in the context of cross-cultural relations during the early centuries CE.

Just as the Sakas migrated to Western and Northwestern India after being driven out of their Central Asian homelands, the Kushans also arrived in Northwestern India after a long migration across Central Asia in the last few centuries BCE. The Kushans were a branch of the Yuezhi, a nomadic group of peoples who inhabited territories near Dunhuang until conflicts with the Xiongnu led to their migration across the Tarim Basin to Bactria between ca. 165-128 BCE. The Yuezhi migrations caused some groups of Sakas to migrate to the Indian subcontinent, when the power of the Indo-Greeks in the northwestern borderlands declined. By the middle of the first century CE, Kushan power extended from Bactria across the Hindu Kush to Gandhara and Taxila (in modern Pakistan).

The first Kushan ruler was Kujula Kadphises, who may be identified with the Yabgu of Guishuang named Qiu Jiuque in Hou Han Shu (128.9). Numismatic evidence shows that Kujula Kadphises continued to imitate posthumous types of coinage of the last Indo-Greek ruler in Central Afghanistan. Other copper coins issued by Kujula Kadphises copy the royal portrait on the obverse from gold coins of the Roman emperor Augustus (31 BCE - 14 CE). The image of the seated Roman emperor is transformed into a Kushan ruler, who is identified as Kujula Kadphises in Greek and Kharosthi legends. As the Kushans progressed further into Northwestern India, Kujula Kadphises adopted the title "Great King, King of Kings" on coins patterned on those of Saka and Parthian rulers. More than 2,500 coins of Kujula Kadphises were found in the latest strata of excavations at the site of Sirkap at Taxila, before the main settlement was shifted to Sirsukh during the period of Kujula Kadphises' successors. Although an absolute chronology is very difficult to establish for the long reign of Kujula Kadphises, numismatic evidence reflects the growth of Kushan hegemony following the reign of the Indo-Parthian ruler Gondophares (after 46 CE).

A Bactrian inscription from Rabatak in Northern Afghanistan helps to clarify the succession of three generations of Kushan rulers following Kujula Kadphises (1). Although the name of Vima Taktu as the direct successor of Kujula Kadphises is not entirely clear, the Rabatak inscription confirms that Kujula Kadphises was followed by another ruler before Vima Kadphises, the father of Kanishka. Vima Taktu can be linked with 'Soter Megas' ("Great Saviour"), the Kushan ruler who issued a series of coins that follow the coin-types of Kujula Kadphises and precede those of Vima Kadphises empire between the time of Kujula Kadphises and Vima Kadphises.

Vima Kadphises introduced the use of gold coinage, perhaps melted down from Roman coins imported to India in exchange for a variety of luxury items. While Roman coins are found in large numbers in Southern India and Sri Lanka, their rarity in Northwestern India may be due to Kushan reminting, begun during the time of Vima Kadphises. Coins issued under Vima Kadphises demonstrate a progression towards more grandiloquent titles and more elaborate iconography than those issued by his Kushan predecessors. Vima Kadphises' coins are also very distinctive because he is portrayed in all his glory as a large man with a huge nose and a wart on one cheek.

The Kushan Empire reached its greatest extent during the reign of Kanishka, whose legacy as a powerful emperor is preserved in inscriptions, textual traditions, archaeological remains, and coins. According to the Rabatak Bactrian inscription, the Kushan realm at the time of Kanishka extended to the cities of Saketa, Kausambi, Pataliputra, and Sri-Campa in the Ganges-Yamuna valley. A colossal statue of Kanishka near Mathura with a Brahmi inscription labeling him "Great King, King of Kings, Son of God, Kanishka" shows that he fulfilled the role of "Universal Emperor" (cakravartin). Buddhist literary sources portray Kanishka as a major patron of Buddhism modelled after the ideal of Asoka (see Mauryan essay). Buddhist imagery appears on some of Kanishka’s coins, but his coins also depict a wide variety of Iranian, Greek, and Indian gods and goddesses.

By the rule of the fifth emperor, Kanishka the Great from 127 to 140 the Kushan Empire had pushed into all of Northern India and expanded east again as far as the Tarim Basin—the original homeland of the Kushans. Kanishka ruled from Peshawar (currently Pakistan), but his empire also included the major Silk Road cities of Kashgar, Yarkand, and Khotan in what is now Xinjiang or East Turkestan.

Kanishka was a devout Buddhist and has been compared to the Mauryan Emperor Ashoka the Great in that regard. However, evidence suggests that he also worshiped the Persian deity Mithra, who was both a judge and a god of plenty.

During his reign, Kanishka built a stupa that Chinese travelers reported as about 600 feet high and covered with jewels. Historians believed that these reports were fabricated until the base of this amazing structure (87 square meter cruciform foundation ) was discovered in Peshawar in 1908. The emperor built this fabulous stupa to house three of the Buddha's bones. References to the stupa have since been discovered among the Buddhist scrolls at Dunhuang, China, as well. In fact, some scholars believe that Kanishka's forays into the Tarim were China's first experiences with Buddhism.

While the evidence from coins and inscriptions at Rabatak and Surkh Kotal clearly shows that the Kushans maintained Iranian religious beliefs and practices, other inscriptions provide abundant evidence of Buddhist patronage by Kushan officials under Kaniska and his successors. Buddhism initially spread from Gandhara and Kashmir via the mountains of Northern Pakistan and the silk routes of the Tarim Basin to China during the period of the Kushans.

The Kushans exerted considerable influence in Tarim Basin oases such as Khotan and Kashgar. According to the Hou Han Shu, between 87-91 CE, a Kushan expedition of 70,000 soldiers crossed the Pamirs to Kashgar because a marriage alliance proposed by a Kushan envoy sent to China was refused. In another episode between 114-119 CE, the Kushans installed their own candidate as the ruler of Kashgar after he returned from exile across the Pamirs. Historical annals of the Wei and other Chinese dynasties also contain references to Chinese relations with the Kushans. Coins of Vima Kadphises and Kanishka and bilingual Chinese and Kharosthi coins issued in Khotan in the first and second century CE provide numismatic evidence for commerce between the Kushan Empire and the Tarim Basin. However, direct control of Eastern Central Asia by the Kushans was unlikely.

The determination of an absolute date for the beginning of the era founded by Kanishka remains unresolved. Since the discovery of the Rabatak inscription, scholarly consensus seems to be shifting away from the traditional date of 78 CE for the beginning of the Kanishka era to an early second century date (ca. 100 CE or one or two decades later). Dating formulae of inscriptions and stylistic analysis of Kushan period sculptures from Mathura and Gandhara suggests that numerals for hundreds were omitted in epigraphic records written during the time of the later Kushan rulers.

After 225 CE, the Kushan Empire crumbled into a western half, which was almost immediately conquered by the Sassanid Empire of Persia, and an eastern half with its capital in Punjab. The eastern Kushan Empire fell at an unknown date, likely between 335 and 350 CE, to the Gupta king, Samudragupta.

Coins during Kushan Dynasty

Still, the influence of the Kushan Empire helped spread Buddhism across much of Southern and Eastern Asia. Unfortunately, many of the practices, beliefs, art, and texts of the Kushans were destroyed when the empire collapsed and if not for the historical texts of Chinese empires, this history may have been lost forever.